Drawing and crimping synthetic polymer filaments



Dec. 27, 1966 w. BlBBY ETAL 3,293,843

DRAWING AND CRIMPING SYNTHETIC POLYMER FILAMENTS Filed Jan. 20, 1964 Attorneys llited States Patent Ofiice 3,293,843 Patented Dec. 27, 1966 3,293,843 DRAWING AND CRlMPlNG SYNTHETIC POLYMER FHLAMENTS Norman William Bibby, Llan-yr-Avon, Cwmbran, John Llewellyn Burgess, Pontypool, Peter John Crabbe, Llanfoist, Abergavenny, and Geoifrey Hugh Jones, Abergavenny, England, assignors to British Nylon Spinners Limited, Pontypool, England Filed Jan. 20, 1964, Ser. No. 338,997 Claims priority, application Great Britain, Feb. 2, 1963, 4,354/ 63 6 Claims. (Cl. 57-157) The present invention concerns improvements in or relating to drawing and crimping synthetic polymer filaments.

Synthetic polymer filaments, such as those of polyamide, polyester and polypropylene materials, are ex truded in an undrawn, straight condition normally by melt-spinning. Subsequent processes of drawing and crimping may then be carried out on the as-spun filaments to orient their molecules and to cause the filaments permanently to adopt a non-linear form when such is the form that is desired.

Such subsequent processes of drawing and crimping may be themselves distinct processes, or they may be combined in one distinct process, subsequent to that of extrusion. Alternatively, both the drawing and the crimping may be carried out on the filaments immediately after extrusion and before they have been wound up.

One way of combining the drawing and crimping processes which has previously been proposed is to impart the drawing tension directly by two meshing toothedwheel members, so that the filaments are forced into a corrugated shape immediately after they have been drawn out into the molecularly-oriented state. The filaments are preferably led several times round one of the toothed- Wheel members and a separator means therefor, so as to make a number of passes between the two members. In another known process, already drawn filaments are crimped by passing them between intermeshing toothedwheel members, preferably heated ones.

We have now discovered that the drawing and crimping processes may be combined in a process utilizing for instance, toothed-wheel members which is not only simpler and safer than that referred to above but also leads to a more desirably crimped product.

According to the process of our invention, undrawn synthetic polymer filaments are heated and pulled under tension to pass once only between means causing the filaments to follow a sharply zig-zag path, the tension so imparted being such that the filaments are molecularly oriented, whereby the filaments are caused to adopt a permanently corrugated shape or crimp, said means having a component of motion in the mean direction of travel of the filaments at the points of contact therewith.

In one embodiment of the invention, the undrawn filaments are advanced by feed rolls to pass in contact with and be heated by a heating means, such as a snubbing-pin or pins, from which means they are drawn by draw rolls under a total tension between said means and said draw rolls sufficient to orient their molecules, and whilst travelling between said means and said draw rolls and whilsthot, e.g. between 100 C. and 160 C., are pulled under tension to pass once only between the intermeshing teeth of a pair of toothed-wheel members rotated at a speed such that the filament speed on passage between the members is less than the surface speed of the draw rolls. The feed rolls and draw rolls referred to may each comprise a main roll with its separator roll, or they may comprise a pair of nip rolls. If, however, nip rolls are employed for the draw rolls it is essential to have the teeth of the said toothed-Wheel members of an involute shape along their meshing sides, as the entire drawing tension will be concentrated at the toothed-wheel members in these circumstances, and involute teeth are essential to enable such tension to be applied without slip.

The process of the-invention may be carried out on the undrawn filaments as a distinct process, or as an intermediate stage of the extrusion and wind-up process.

It is desirable that the toothed-wheel members of the embodiment are maintained at a uniform temperature so that they shall not become gradually heated by contact from the hot filaments and thus be responsible for nonuniform crimping conditions along a length of the filaments. This may have to be achieved by a blast of air directed upwardly into their meshing area, or directed solely against one of the members. The propensity to heat-up will however be less with stainless'steel than with brass members, although brass members may be preferred for general crimp quality. The frequency of the crimp may be adjusted by altering the number of teeth per inch in the members, and the amplitude altered by increasing or decreasing the meshing engagement of the teeth.

In certain cases, also, the filaments themselves on emergence from the toothed-wheel members are desirably cooled to help set the crimp. This may be achieved by directing a blast of air directly on to them after their emergence, either with or without also impinging on to either or both of the members.

The fact that the filaments are pulled between the teeth of the toothed-wheel members under tension has two main advantages. Firstly, the crimp thereby imparted to the filaments is enhanced, compared with those processes in which the toothed-wheel members alone impart the whole drawing tension or in which already drawn filaments are passed between toothed-wheel members. Secondly, the apparatus is simplified compared with that required for the process in which the toothed-wheel members impart the whole drawing tension; and, because it is not necessary, as in the latter cases, to pass the filaments between the members with a plurality of passes, it is possible and simple to guard the members. and hence the apparatus is safer.

The former advantage appears to result from the facts that the continuous deformation of the filaments occurs whilst they are themselves under tension both leading towards and away from the toothed-wheel members; and that, with a single pass, there is less heating-up of the members by the filaments.

The latter advantages arise from the ability to utilize the ordinary means for drawing, including the drawroll/ separator-roll system for non-slipping engagement of the filaments, and hence the ability to employ simple toothedwheel members, such as straight spur gear wheels, rather than the more complicated tapered ones required to accommodate a plurality of passes by the filaments in order to achieve the required non-slipping engagement for uniform drawing directly by such tapered gear wheels.

It is preferred to use gear wheels as the toothed-wheel members; and gears of around 3 inches in diameter, with between about 7 and about 20 teeth per inch, are suitable for crimping heavy and medium denier multifilament nylon yarns.

It is highly advantageous to use involute teeth for the gears, as this shape allows for the driving of onegear by the other with a smooth transmission of rotary motion. Thus, the mechanical problems are greatly eased, as the drive has only to be to one gear, and there is no requirement for matching the rotary speeds of the two gears. Gear intermeshes of 35, 40 and thousandths of an inch have been employed with such involute teeth of thousandths of an inch depth.

' gear only being driven and driving the other.

The teeth may be regular in size and spacing around the gear; or, if novelty effects are required, the spacing may be irregular (the two gears being matched in this respect) or the amplitude of the teeth may be varied around the gear.

Normally, however, regular spacing and amplitude of the teeth is desirable, but some de-phasing of the ciim'p is usually subsequently required as by the imparting of twist or false twist to the yarn before it is wound up. Some degree of out-of-phase in the crimp may be attained if the teeth are helieally arranged around the periphery of the gear wheel, rather than with their tips parallel to the axis thereof. Preferably, with any shaped teeth, the tips are rounded.

The yarn may be led directly to the meshing area of the gears; or it may be led so as to make a partial wrap around the periphery of one gear before entering the meshing area.

The temperature of the yarn whilst being crimped is fairly critical. To be effective, the temperature must be at least about 100 C. for most synthetic polymer materials; and above about 140 C. the temperature appears to have no significant effect on the crimp in yarn of polyhexamethylene adipamide, and consequently economic and working conditions suggest that 140 C.-l60 C. should be the optimum range in practice. Naturally, the temperature of the heating means, such as a snubbing pin, will normally have to be slightly higher than the desired yarn temperature at crimping.

The above described embodiment of the invention will now be described by reference to the accompanying drawing, which is a diagram showing the yarn path through and around the sundry items of apparatus incorporated in this embodiment.

In the drawing, undrawn filaments in the form of yarn Y are withdrawn over one end of a supply package 1 through a pig-tail guide 3 by means of nip feed rolls 5, 7. The yarn is then drawn within the span between feed rolls 5, 7 and draw roll 9 with separator roll 11. Within this span is also situated snubbing pin 13, electrically heated via wires 15 and around which the yarn is wrapped by two turns. Between the said snubbing pin 13 and the draw roll 9, the yarn is pulled between gear wheels 17, 19, one or both of which is or are driven by means not shown at a speed such that the yarn speed through the gear wheels is less than the surface speed of the draw roll. On departure from the draw roll 9 and its separator roll 11, the yarn Y now fully drawn, is wound on a ring spindle package 21, twist being inserted in the yarn below balloon-guide 27, by virtue of the rotation of the spindle and of the rotation of traveller 23 around ring 25.

The following examples indicateprocessing conditions and yarn and fabric properties for certain synthetic polymer filaments, when such are processed according to the above embodiment of the invention.

Example I The supply yarn was 3600 denier (undrawn) 68 filament multifilament yarn of polyhexamethylene adipamide, the filaments whereof had a triangular cross-section. The apparatus employed was similar to that illustrated in the drawing, the snubbing pin being heated to 160 C. and the gear wheels being of 3-inch pitch diameter and having 150 involute teeth, 15 to the inch, one The whole depth of the teeth was 55 thousandths of an inch and the intermesh was 45 thousandths of an inch. The circular tooth thickness at the pitch line was 30 thousandths of an inch; and the angle between the sides of adjacent teeth was 40. The gear wheels were A, inch thick.

De-phasing of the regular planar crimp, in the crimped,

' drawn yarns, then of 1040 denier, was accomplished by superimposing a small amount of false twist crimp over 4 the primary gear crimp, by passing the drawn yarn in frictional contact with a false-twist imparting flange, fitted to one end of the drawroll, like that described in our British patent specification No. 890,05 3-.

The other processing conditions were as follows:

Feed roll speed 3 94 feet/minute (surface speed). Gears speed 1080 revolutions/ minute. Draw roll speed 1380 feet/minute (surface speed). Draw ratio 3.5.

The crimped, drawn yarn which had a skein length of 16 inches, was three-folded and tufted to form the pile of a loop-pile carpet. The carpet was piece-dyed, and the latent bulk of the crimped yarn was thereby developed. The carpet had an excellent handle and cover.

Example II The apparatus employed in this instance was similar to that of Example I, save that the gears had 20 involute teeth to the inch.

The yarn was a multifilament yarn of polyhexamethylene adipamide, the filaments being of triangular crosssection, of 400 drawn denier.

The processing conditions were the same as those of Example I, save for the following:

Feed roll speed 500 feet/minute (surface speed).

Gears speed 1,700 revolutions/ minute.

Draw roll speed 2,000 feet/minute (surface speed).

Draw ratio 4.0.

The crimped, drawn yarn, which had a skein length of 16 inches was knitted into a fabric with a full cardigan stitch, and the latent bulk of the yarn was developed during piece-dyeing. The fabric had good stitch clarity, rib regularity, recovery from extension and depth of handle.

Example III Feed roll speed 286 feet/minute (surface speed). Gears speed 840 revolutions/ minute. Draw roll speed 1,000 feet/minute (surface speed). Draw ratio 3 5 The crimped, drawn yarn was very suitable for knitted outerwear.

Example IX The yarns were multifilament yarns of polyhexamethylene adipamide having 68 filaments of trilobal cross-section of 3600 denier in the undrawn state. The yarn was heated by a wrap around a snubbing-pin heated to C. and brass gears having 38 straight-sided teeth with 7.1 teeth per linear inch were each independently driven and were cooled by a blast of air directed upwardly into their nip, the gear and roll speeds and the yarn speeds and tensions measured at the sundry positions along the threadline were as follows:

Feed roll surface speed 165 feet/minute. Gear wheels surface speed 390 feet/minute. Draw roll surface speed 620 feet/minute. Yarn tension between snubbing-pin gear wheels 552 feet/minute Yarn speed between gear wheels and draw roll 585 feet/minute. Yarn speed between draw roll and wind-up 554 feet/minute. Yarn tension between snubbing-pin and gear wheels 870 grams. Yarn tension between gear wheels and draw roll 440 grams.

The yarn so drawn and crimped had the following properties making it suitable for use in carpets:

Skein length 16.8.

Crimp ratio 0.047.

Crimp frequency 6.1 crimps per inch. Drawn yarn denier 997.

Drawn yarn tenacity 3.65 grams per denier Drawn yarn extensibility 43.1%.

Drawn yarn crimp retentivity 72.3%.

In the above examples, the skein length Was measured by the conventional method in which a skein of yarn is made by winding 45 wraps on a 54-inch diameter wrap wheel under a tension just sufficient to straighten the yarn. The skein is then suspended in water at 60 C. and the skein length measured under a tension of 16 grams.

Crimp frequency is defined as the average of counts of the number of crirnps per inch under a tension of 1 milligram per denier.

In addition to the filaments specified in the examples, other synthetic polymer filaments may be drawn and crimped according to the invention. For example, polycaprolactam and polypropylene filaments may be so treated, in the latter instance heating of the feed rolls also being advantageous.

Instead of a heated snubbing pin being used to impart heat to the yarn, a heated plate may :be substituted, for instance. Again, more than one yarn may be passed simultaneously between the gear wheels, and the yarns either wound up together or separately.

Finally, although the above-described and illustrated embodiment makes use of driven toothed-wheel members to cause the yarn to follow the sharply zig-zag path, it is to be understood that any other means attaining the same result may be employed, provided that such means also has a component of motion in the mean direction of travel of the filaments at the points of contact therewith. Thus, meshing corrugated bands could be employed instead of toothed-wheel members.

6 What we claim is: 1. A process for drawing and crimping synthetic polymer filaments comprising the steps of (a) positively advancing undrawn synthetic polymer filaments from a supply thereof, (b) heating said filaments. (c) subjecting said heated undrawn filaments to a drawing tension, (d) imparting a crimp to said heated filaments whilst they are hot and whilst they are under the drawing tension by passing them once only between means causing the filaments to follow a sharply zig-zag path, said means having a compoennt of motion in the mean direction of travel of the filaments at the points of contact therewith, and (e) pulling the crimped and drawn filaments under tension away from said means. 2. A process according to claim 1 in which said means comprises a pair of intermeshing gear wheels.

3. A process according to claim 1 in which the filaments are heated to a temperature between C. and C.

4. A process for drawing and crimping synthetic polymer filaments comprising the steps of (a) imparting a regular planar crimp to said filaments whilst they are heated and whilst they are undergoing drawing, by passing them once only between means causing the filaments to follow a sharply zig zag path, said means having a component of motion in the mean direction of travel of the filaments at the points of contact therewith, (b) pulling the crimped and drawn filaments under tension away from said means, and (c) de-phasing said regular planar crimp by imparting a false twist to said crimped and drawn filaments. 5. A process according to claim 4 in which the false twist is imparted by friction.

6. A process according to claim 5 in which the friction is derived from a flange on one end of a draw roll employed to pull the filaments from said means.

References Cited by the Examiner UNITED STATES PATENTS 2,030,252 2/ 1936 Hale et al. 2872 2,321,726 6/1943 Alderfer 57-168 2,988,799 6/ 1961 Atwell 2872 3,024,516 3/ 1962 Bromley et al. 281 3,041,706 7/1962 Bromley et al 281 3,094,834 6/1963 Deeley et al. 57157 3,124,628 3/1964 Hughey 57-157 3,192,597 7/ 1965 McIntosh et a1 281 STANLEY N. GILREATH, Primary Examiner.

FRANK I. COHEN, Examiner.

J. PETRAKES, Assistant Examiner. 

1. A PROCESS FOR DRAWING AND CRIMPING SYNTHETIC POLYMER FILAMENTS COMPRISING THE STEPS OF (A) POSITIVELY ADVANCING UNDRAWN SYNTHETIC POLYMER FILAMENTS FROM A SUPPLY THEREOF, (B) HEATING SAID FILAMENTS. (C) SUBJECTING SAID HEATED UNDRAWN FILAMENTS TO A DRAWING TENSION, (D) IMPARTING A CRIMP TO SAID HEATED FILAMENTS WHILST THEY ARE HOT AND WHILST THEY ARE UNDER THE DRAWING TENSION BY PASSING THEM ONCE ONLY BETWEEN MEANS CAUSING THE FILAMENTS TO FOLLOW A SHARPLY ZIG-ZAG PATH, SAID MEANS HAVING A COMPONENT OF MOTION IN THE MEAN DIRECTION OF TRAVEL OF THE FILAMENTS AT THE POINTS OF CONTACT THEREWITH, AND (E) PULLING THE CRIMPED AND DRAWN FILAMENTS UNDER TENSION AWAY FROM SAID MEANS.
 4. A PROCESS FOR DRAWING AND CRIMPING SYNTHETIC POLYMER FILAMENTS COMPRISING THE STEPS OF (A) IMPARTING A REGULAR PLANAR CRIMP TO SAID FILAMENTS WHILST THEY ARE HEATED AND WHILST THEY ARE UNDERGOING DRAWING, BY PASSING THEM ONCE ONLY BETWEEN MEANS CAUSING THE FILAMENTS TO FOLLOW A SHARPLY ZIGZAG PATH, SAID MEANS HAVING A COMPONENT OF MOTION IN THE MEANS DIRECTION OF TRAVEL OF THE FILAMENTS AT THE POINTS OF CONTACT THEREWITH, (B) PULLING THE CRIMPED AND DRAWN FILAMENTS UNDER TENSION AWAY FROM SAID MEANS, AND (C) DE-PHASING SAID REGULAR PLANAR CRIMP BY IMPARTING A FALSE TWIST TO SAID CRIMPED AND DRAWN FILAMENTS. 